1. Field of the Invention
The present embodiments relate to compounds with physiological effects, such as the activation of hematopoietic growth factor receptors. The present embodiments also relate to use of the compounds to treat a variety of conditions, diseases and ailments such as hematopoietic conditions and disorders.
2. Description of the Related Art
Hematopoietic growth factor (HGF) represents a family of biological molecules such as glycoproteins with important regulatory functions in the processes of proliferation, differentiation, and functional activation of hematopoietic progenitors and mature blood cells. HGF compounds can be potent regulators of blood cell proliferation and development in the bone marrow. They are able to augment hematopoiesis when bone marrow dysfunction exists. Recombinant DNA technology has made it possible to clone the genes responsible for many of these factors.
One example of an HGF is Thrombopoietin (TPO), also referred to as c-Mpl ligand, mpl ligand, megapoietin, and megakaryocyte growth and development factor, is a glycoprotein that has been shown to be involved in production of platelets. See e.g., Wendling, F., et. al., Biotherapy 10(4):269-77 (1998); Kuter D. J. et al., The Oncologist, 1:98-106 (1996); Metcalf, Nature 369: 519-520 (1994), all of which are incorporated herein by reference in their entirety. TPO has been cloned and its amino acid sequence and the cDNA sequence encoding it have been described. See e.g., U.S. Pat. No. 5,766,581; Kuter, D. J. et al., Proc. Natl. Acad. Sci., 91:11104-11108 (1994); de Sauvage F. V., et al., Nature, 369: 533-538 (1994); Lok, S. et al., Nature 369:565-568 (1994); Wending, F. et al., Nature, 369: 571-574 (1994), all of which are incorporated herein by reference in their entirety.
In certain instances, TPO activity results from binding of TPO to the TPO receptor (also called MPL). The TPO receptor has been cloned and its amino acid sequence has been described. See e.g., Vigon et al., Proc. Natl. Acad. Sci., 89:5640-5644 (1992), which is incorporated herein by reference in its entirety.
In certain instances, TPO modulators may be useful in treating a variety of hematopoietic conditions, including, but not limited to, thrombocytopenia. See e.g., Baser et al. Blood 89:3118-3128 (1997); Fanucchi et al. New Engl. J. Med. 336:404-409 (1997), both of which are incorporated herein by reference in their entirety. For example, patients undergoing certain chemotherapies, including but not limited to chemotherapy and/or radiation therapy for the treatment of cancer, may have reduced platelet levels. In certain instances, treating such patients with a selective TPO modulator increases platelet levels. In certain instances, selective TPO modulators stimulate production of glial cells, which may result in repair of damaged nerve cells.
Another example of an HGF is the glycoprotein hormone erythropoietin (EPO). EPO is an essential viability and growth factor for the erythrocytic progenitors. EPO is a member of the family of class I cytokines which fold into a compact globular structure consisting of 4 α-helical bundles. Its molecular mass is 30.4 kDa, although it migrates with an apparent size of 34-38 kDa on SDS-polyacrylamide gels. The peptide core of 165 amino acids suffices for receptor-binding and in vitro stimulation of erythropoiesis, while the carbohydrate portion (40% of the total molecule) is required for the in vivo survival of the hormone. The 4 carbohydrate chains of EPO have been analyzed in detail. The 3 complex-type N-linked oligosaccharides at asparagines 24, 38 and 83 appear involved in stabilizing EPO in circulation. EPO is mainly produced by hepatocytes during the fetal stage. After birth, almost all circulating EPO originates from peritubular fibroblast-like cells located in the cortex of the kidneys. Transcription factors of the GATA-family may be important in the control of the time-specific and tissue-specific expression of the EPO gene. In adults, minor amounts of EPO mRNA are expressed in liver parenchyma, spleen, lung, testis and brain. In brain, EPO exerts neurotrophic and neuroprotective effects, which are separate from the action of circulating EPO on erythropoietic tissues. See e.g., Jelkmann, W., Internal Medicine Vol. 43, No. 8 (August 2004).